1. Field of the Invention
The present invention relates generally to a monitor for determining the amount of moisture in fluids, and more particularly to a monitor for determining the amount of moisture in liquids as express in parts per million by weight PPM.sub.W.
2. Description of the Prior Art
Liquids consisting of nonpolar molecules such as hydrocarbon chains in oils or hydrocarbon rings in benzene, toluene, etc. do not mix with water. Similar to gases, liquid hydrocarbons can absorb a certain amount of water vapor and thus have a moisture concentration or saturation value. In contrast to gasses, liquids have individual saturation values. These values are temperature dependent and raise with increasing temperature. The similarity of non polar liquids to gasses allows moisture measurement with the gold/aluminum oxide sensor since the measurement is only influenced by the water molecules.
Numerous analytical techniques have been suggested for the determination of moisture in liquids. The majority of the commonly used methods are batch techniques, and require sample collection and transfer prior to laboratory analysis. The most generally used procedures employ the "Karl Fischer" reagent. This has become the accepted method of water determination. Although the "Karl Fisher" method has wide acceptance, several limitations have indicated the need for more reliable methods. There is a necessity to withdraw a sample from a fluid line, in a separate container which is free from adverse atmospheric conditions. Transferring this container to the laboratory and finally transferring the sample to another container creates exposure to strong oxidizing or reducing agents. The detection of the Karl Fischer end point requires careful technique and experience if the method is to provide reliable analyses.
The standard ASTM test for water, D1533, which involves the use of jars, has the disadvantage that the oil sample comes in contact with the atmosphere both at the time of sampling and at the time of analysis. Since moisture is present in atmospheric air, there is always the chance that the sample will become contaminated and an inaccurate result obtained. For these reason, the use of glass or plastic jars as sampling containers must be avoided.
Moisture content verification using the jar method of sampling cannot verify accuracy of 1 to 15 PPM.sub.W.